Disk drives are widely used in computers, consumer electronics and data processing systems for storing information. The disk drive typically includes one or more storage disks and one or more slider assemblies. Each slider assembly includes a read/write head that transfers information to and from the storage disk. Rotation of the storage disk causes the slider assembly to ride on an air bearing with the read/write head spaced apart from the storage disk a distance that is commonly referred to as a “head-to-disk spacing”.
Because today's disk drives utilize storage disks having increasingly high densities of data tracks, decreasing the head-to-disk spacing has become of great importance. However, this desire for a very small head-to-disk spacing must be balanced with tribological concerns in order to avoid damage to the read/write head and/or the storage disk, as well as loss of data.
Maintaining a relatively small and consistent head-to-disk spacing is further complicated by other factors. In particular, the read/write head includes a write element. During a write operation, the electrical resistance in the write element generates heat in and around the read/write head. The heat causes thermal expansion of portions of the slider assembly toward the storage disk, known as write pole tip protrusion (“WPTP”). In addition, environmental temperature increases within the disk drive can also result in environmental pole tip protrusion (“EPTP”) toward the storage disk. If pole tip protrusion is excessive, the slider assembly can unintentionally contact the storage disk (“head-to-disk contact”), causing off-track writing, degraded data transfer rates, damage to the slider assembly, damage to the storage disk and/or a permanent loss of data.
Conversely, a temperature decrease in the drive will induce the opposite effect on the EPTP—the pole tips will retract from the disk. Such retraction can degrade the performance of the reading and writing process since larger spacing can generally degrade the information transfer to and/or from the disk.